Chapter 13: Ethers and Thiols

Question 1

Common naming of ethers

Answer 1

Common name is constructed by:

1. Identifying each R group
2. Arrange them in alphabetical order
3. Add the word ether to the end of the word

Question 2

Systematic naming of ethers

Answer 2

Systematic name is constructed by:

1. Identify the larger group as the parent chain
2. Name the smaller group as an alkoxy substituent
3. Locants are assigned so as to give the lowest possible numbers

Question 3

Naming of crown ethers

Answer 3

Use the formula X-crown-Y

• X indicates the total number of atoms in the ring
• Y represents the number of oxygen atoms

Question 4

Crown ether solvable ions

Answer 4

Question 5

Williamson synthesis

Ethers

Answer 5

Reagents

1. NaH (sodium hydride)
2. RX

Mechanism

Starting with an alcohol as substrate, the hydride ion deprotonates the hydroxyl group with the alkyl halide subsequently attacking the negatively charged oxygen

Alkyl halide must be a methyl or primary alkyl halide to favor S_N2 reaction

Question 6

Alkoxymercuration-Demurcuration

Answer 6

Reagents

1. Hg(OAc)₂ (mercuric acetate) & ROH
2. NaBH₄ (sodium borohydride)

Mechanism

Markovnikov addition of an alcohol (RO and H) across an alkene; RO alkoxy substituent added to the more substituted vinylic carbon

Question 7

Acidic cleavage

Ether

Answer 7

Reagents

excess HX (hydrogen halide) & heat

Mechanism

Ether is converted into two alkyl halides

When a phenyl ether is cleaved under acidic conditions the products are an phenol and an ether; only applies to phenyls, NOT cyclic alkanes

Question 8

Autooxidation

Ether

Answer 8

Ethers undergo autooxidation in the presence of atmospheric oxygen to form hydroperoxides

Question 9

Naming of epoxides

Answer 9

Question 10

Preparation of epoxides

Answer 10

Reagents

RCO₃H (peroxy acid)
MCPBA

or

1. Br₂ & H₂O
2. NaOH

Mechanism

Epoxides can be prepared using an alkene as a substrate upon treatment with a peroxy acid such as MCPBA or through a halohydrin intermediate

Question 11

Sharpless asymmetric epoxidation

Answer 11

Reagents

tBuOOH (tert-Butyl hydroperoxide)
Ti[OCH(CH₃)₂]₄ (titanium tetraisopropoxide)
(+)-DET or (−)-DET

Mechanism

Enantioselective epoxidation process that produces only one enatiomer

Question 12

Ring-opening reaction of an epoxide

Strong nucleophile

Answer 12

Reagents

1. Stong Nuc
2. H₃O⁺

Question 13

Ring-opening reaction of an epoxide

Acid-catalyzed

Answer 13

Reagents

HX (hydrogen halide)

or

H₃O⁺ & H₂O

or

H₃O⁺ & ROH

Question 14

Controlling the location of a functional group addition

Grignard reagents

Answer 14

Question 15

Naming thiols

Answer 15

Question 16

Preparation of thiols

Answer 16

Question 17

Converting between disulfides and thiols

Answer 17

Question 18

Naming of sulfides

Answer 18

Question 19

Preparation of sulfides

Answer 19

Question 20

Sulfide addition

Answer 20

Question 21

Oxidation of sulfides

Answer 21